1. Field of the Invention
The invention relates to a polymer having stilbenquinone structures as a repetitive unit and an electrophotographic photoreceptor containing the same. More particularly, the invention relates to a polymer with an improved electro-transporting capacity, in that precipitation does not occur even when used as an electron transporter for an electrophotographic photoreceptor in a high concentration, and an electrophotographic photoreceptor containing the polymer.
2. Description of the Related Art
Generally, an electrophotographic photoreceptor is produced by forming a photosensitive layer containing a charge generating material, a charge transporting material and a binder resin on an electroconductive substrate. Typically, a laminated-type photoreceptor with separate functional layers is used, in which a charge transporting material and a charge generating material are laminated to produce a photosensitive layer.
Recently, however, there have been active research and developments on single layered photoreceptors, which have the advantages of having a simple production process and having positive chargeability available to a positive corona discharging, which is a weak ozone producing mechanism.
Examples of single layered photoreceptors are a photoreceptor containing PVK/TNF charge transporting complex as disclosed in U.S. Pat. No. 3,484,237, a photoreceptor containing photoconductive phthalocyanine as disclosed in U.S. Pat. No. 3,397,086 and a photoreceptor which contains thiapyrylium dye salt and a charge transporting material as disclosed in U.S. Pat. No. 3,615,414. However, such photoreceptors are not presently used because the photoreceptors have disadvantages of unsatisfactory electrostatic characteristics, restrictive selection of suitable materials, and toxicity of materials.
Most of the widely used single layered photoreceptors have a photosensitive layer produced by dispersing a charge generating material disclosed in Japanese Laid-Open Publication 54-1633, a hole transporting material and a electron transporting material in a binder resin. Such a photoreceptor has the advantage of allowing a wide selection of materials because of the separation of functions between the charge generating material and the charge transporting material. Also, the charge generating material may be used in a low concentration, helping to enhance the functional and the chemical stability of the photoreceptor.
However, because the electron transporting material used for the aforementioned photoreceptor is ordinarily a monomolecular material, such as diphenoquinone of Chemical Formula I or stilbenquinone of Chemical Formula II, high concentrations of the materials are necessary to obtain a high electron transportability. These monomolecular electron transporting materials have limited solubility in a binder resin, and thus form precipitates which are deposited on the film during a film forming process.

In an attempt to overcome the foregoing problems, U.S. Pat. No. 6,228,546B1 disclosed a polymer with a diphenoquinone structure as a repetitive unit as represented by Chemical Formula III.

However, in order to synthesize the polymer of Chemical Formula III, a high priced catalyst and reactants such as Fetizon reagent are used, thus, depreciating the cost efficiency. Also, it is difficult to obtain a polymer with a high molecular weight due to side reactions of the materials.